1. Field of the Invention
The present invention relates to systems for reducing rotational nonuniformities of shafts and in particular a draft shaft of an internal combustion engine.
2. Description of the Related Art
The invention concerns a system for actively reducing rotational nonuniformity of a shaft, especially the drive shaft of an internal combustion engine or a shaft which is coupled or can be coupled to it.
More simple systems of this type are known, which can only act by driving or only by braking an internal combustion engine to reduce its rotational nonuniformity. Thus, Patent Abstracts of Japan, Volume 11, No. 28 (M-557), Jan. 27, 1987 & JP-A-61 200 333 (NISSAN I) discloses a synchronous electrical machine that is directly coupled to the crankshaft of an internal combustion engine and is switched like a (driving) electric motor when the rotational speed falls below a certain standard value and thus counteracts a rotational nonuniformity to slow down (a so-called negative rotational nonuniformity). The motor is shut off when the rotational speed goes beyond this standard value.
A purely brake type system is disclosed by Patent Abstract of Japan, Volume 4, No. 29 (M-002), Mar. 14, 1980 & JP-A-55 005 454 (TOYOTA). Here, an electromagnet surrounds the outer rim of a flywheel on the crankshaft of an internal combustion engine. The electromagnet is excited synchronously with rotational nonuniformities and thus brakes the flywheel in correct phase, acting like an eddy current brake.
Similarly, EP-B-0 427 568 (ISUZU) discloses an internal combustion engine with a conventional belt-driven dynamo, which acts like a brake when there is a rotational nonuniformity to speed up (a so-called positive rotational nonuniformity). Finally, DE-A-32 30 607 (VW I) also discloses an internal combustion engine with a flywheel-dynamo, which acts like a brake when there is a rotational nonuniformity during phases of positive nonuniformity. The dynamo can also serve as a starter for the internal combustion engine.
Systems which can alternately act as drives and brakes to actively reduce rotational nonuniformities are also known in the state of the art:
Thus, EP-B-0 175 952 (MAZDA) discloses such a system with a commutator machine, having two stator windings- one for driving and one for braking. Through alternating correct-phase excitation of these two stator winding ,the machine alternately behaves like a drive and a brake.
Patent Abstracts of Japan, Volume 7, No. 240 (M-25), Oct. 25, 1983 and JP-A-58 126 434 (NISSAN II) disclose a system with a commutator machine, wherein the electrical energy obtained here by braking is saved in a capacitor and again used for driving.
DE-A-41 00 937 (FICHTEL & SACHS) discloses a system with a synchronous alternating current machine, which can generate a torque with periodically changing direction. The synchronous machine is configured such that the torque fluctuations occur in a fixed phase position relative to the crankshaft, so that they can counteract certain rotational nonuniformity orders of the internal combustion engine. But in order to allow a certain adjustment of this fixed phase relationship, the stator winding arrangement of the synchronous machine can have several winding strands laid down in opposite peripheral direction, which can be optionally energized with current.
These known systems essentially enable an active reduction of rotational nonuniformity.
More remote state of the art shall also be mentioned below, pertaining to certain configurations of the invention:
EP-A-0 604 979 (NIPPONDENSO) discloses an active vibration dampening system, in which a direct current machine furnishes alternating moments phase-shifted to rotational nonuniformities, in order to dampen vibrations of the vehicle in this way.
EP-A 0 437 266 (MAGNET-MOTOR) and DE-A 33 35 923 (VW II) disclose flywheel accumulators for hybrid vehicles.
DE-A 33 38 548 (VW II), DE-A 44 08 719 (VW IV), DE-A 0 938 680 (MULLER), DE-A 0 282 671 (MEYER) and U.S. Pat. No. 2,790,917 (TROFIMOV) concern electromagnetic couplings.
DE-A 32 43 513 (VW V) discloses an electric machine in whose proximity a mechanical coupling is arranged.
H. Deisenroth, C. Trabert: "Avoidance of Voltage Surge in Pulse Invertor Drives," etc., 1993, 1060, concerns pulse invertor drives.
DE-A 42 30 510 (GRUNDL & HOFFMANN) and W. Geissier, F. Unger-Weber: "Modeling the Three-Phase Propulsion System of a Modern Multisystem Locomotive," EPE, Florence, 1991, 4-632, disclose liquid-cooled invertor.
J. Langheim, J. Fetz: "Electric Citybus with Two Induction Motors--Power Electronics and Motor Control," ETEP, Vol. 2, No. 6, November/December 1992, 359, concerns a field-oriented regulation of an electric machine.